Not exactly. It does turn on... Just not always.

Details -

Intel E7500 CPU
Intel DG35EC Mbd
XFX Nvidia 9400 GT graphics
2x HD's(1 tb + 500 gbs)
Windows XP

This is how it starts...
1. I try to turn it on. It doesn't. This goes on for about 10 minutes, in which I turn the plug on and off a few times and pushing the power button. Keep trying.
2. I open up the cabinet, pull out the CMOS jumper and Battery. Re-position the jumper. Check for the MBd's LED for power. Check connections, any loose cables.
3. Once it feels like it.. It turns on, but won't do anything. Just powers up. The hard-disk have powered-up (I can hear them humming) bu it doesn't boot. No monitor signal EITHER.
4. I repeat Step 3 and plug out my Hard drives and DVD drive...and try to power on. If I m lucky, it will power on and then I'll have to set things up and again. And then try starting it this time again...With HD's and hope it boots which, after a few 'non-booting' power ups and tries, it does.

So basically...There's like a 15-20 foreplay before it starts up. In which, I have to check things, WATCH it power up without Boot and eventually..Power up normally.

I have CHANGED the CMOS battery. But tonight, it showed up an error of CMOS Battery checksum error when it booted. I hit the reset button and NEXT time it booted fine. Any idea why its being moody like this? Been happening for about 2-3 weeks now.Disconnect everything from the motherboard, except PSU, graphics card, monitor, & keyboard.  See if it will POST.Tried that first thing computer Commando_Commando.

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Update...

I was wrong. It wasn't my fiddling that was turning the computer on...

I have googled this and most people say it's a PSU issue. But Im gonna get some more view before I jump to buying a new one.

What happens is...the Computer doesn't 'turn on' on pressing the 'Power On' button. After the press, it waits for about 10-15 minutes and then spontaneously starts to turn on... I says 'starts to' because it doesn't start booting. I can hear the Hard disks humming but the red LED's for hard disk read don't light as they do when computer starts loading the OS. Then in 2-3 more minutes it boots. The boot itself is not delayed at all. After this initial delay...the computer works flawlessly.

Power Button Press >> Delay of 10-15 minutes >> Spontaneous Power Up >> But No Boot (Only green LED for Power) >> 2-3 mins >> Spontaneously begins Booting. (red LED's for HD read and booting) Quote from: LykanthricAura on July 08, 2012, 03:09:32 PM

...I have changed the CMOS battery. But tonight, it showed up an error of CMOS Battery checksum error when it booted. I hit the reset button and next time it booted fine...

...Power Button Press >> Delay of 10-15 minutes >> Spontaneous Power Up >> But No Boot (Only green LED for Power) >> 2-3 mins >> Spontaneously begins Booting. (red LED's for HD read and booting)